Interaction of formal design systems in the development of a fault-tolerant clock synchronization circuit

We propose a design strategy that exploits the strengths of different formal approaches to establish a reliable path from a mechanically verified high-level description to a concrete gate-level realization. We demonstrate the use of this approach in the realization of a fault-tolerant clock synchronization circuit. We used the Digital Design Derivation system (DDD) to derive a major portion of the design leaving relatively small portions to be verified either by use of a mechanical theorem prover (PVS) or by demonstrating boolean equivalence using Ordered Binary Decision Diagrams. The interface between the different formal systems has not yet been completely formalized but we believe our approach will provide an effective formal design path from high-level specifications to concrete realizations